In order to mechanically and/or electrically and/or thermally join a metallic component with a metallic component, solder, a silver paste, an anisotropically conductive film and the like are used. These anisotropically conductive adhesive, silver paste and anisotropically conductive film are not only for joining metallic components, but can be used for joining a ceramic component(s), a resin component(s) and the like. For example, joining of a light-emitting element, such as LED, to a substrate, joining of a semiconductor chip to a substrate, further joining of the substrates to a heat dissipation member and the like are exemplified.
Among them, an adhesive including solder and a conductive filler made from metal, a paste and a film are used for joining at a portion requiring electric connection. In addition, since metal has high thermal conductivity in general, these additive including solder and a conductive filler, paste and film may be used in order to increase heat dissipation, as well.
In the meantime, for example, when an illumination device or a light-emitting device with high intensity is manufactured using a light-emitting element, such as LED, or when a semiconductor device is manufactured using a semiconductor element that is referred to as a power device to efficiently run at a high temperature, a caloric value tends to rise. Although an attempt to improve an efficiency of the device or the element to reduce heat generation is conducted, a sufficient result has not been achieved under the present circumstances, and it is in the present situation where the operating temperature of the device and the element is increased.
Further, from a viewpoint to prevent damage to the device upon joining, a joint material that can secure sufficient joint strength at a low joining temperature (for example, 300° C. or less) is in demand. Therefore, although thermal resistance to withstand a decrease in a low joining temperature, and, a rise of operating temperature due to operation of the device after being joined and to enable the maintenance of sufficient joint strength is in demand in a joint material for joining a device, an element or the like, but conventional joint materials often cannot handle the situation under such conditions sufficiently. For example, solder joins members via a process to heat metal to its melting point or higher (reflow process), and since a melting point is unique to its composition in general, if a heatproof temperature is attempted to be increased, a heating (joining) temperature is also increased.
In addition, when several layers of elements or substrates are superposed and joined using solder, it is necessary to be via heating process by the number of times equal to the number of layers to be superposed, and in order to prevent fusion of the already joined parts, it is necessary to reduce a melting point (joining temperature) of the solder that is used in the next joining, and the number of types of solder composition equal to the number of the layers to be superposed becomes required, and handling becomes complicated.
In the other hand, in a conductive adhesive, a silver paste and an anisotropically-conductive film, although members are joined by utilizing thermal curing of epoxy resin or the like to be contained, if the operating temperature of the obtained device or element is increased, the resin component can be decomposed or deteriorated. For example, in Patent Literature 1 (Japanese Patent Application Laid-Open No. 2008-63688), particulates that are designed to obtain higher joint strength when members to be joined are joined using a chief material of the joint material has been proposed, but a problem about decomposition or deterioration of a resin component at the time of increasing the operating temperature has not been eliminated yet.
Further, solder containing lead has been conventionally used for high-temperature solder that is used at a high operating temperature. Since lead has toxic properties, a trend to lead-free solder is remarkable. Since there is no other alternative material for the high-temperature solder, lead solder is still used, but a joint material without using lead is desired from a viewpoint of environmental issues.
Recently, as an alternative material for the high-temperature solder, a joint material using metallic nanoparticles focus upon noble metals, such as silver or gold, has been developed (for example, Japanese Patent Application Laid-Open No. 2012-046779). However, in order to accomplish joining using the metallic nanoparticle is accomplished, it is necessary to perform pressure joining under inert atmosphere at 300° C. to 350° C., and a decrease in a joining temperature and no pressurization are issues.